Pictures: Prehistoric American Skull Found in Sea Cave?

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Pictures: Prehistoric American Skull Found in Sea Cave?

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First American?

Divers carefully place a marker near a human skull found upside down in a large underwater cave near the Caribbean Sea on Mexico's Yucatán Peninsula (map) in 2007.

Based on the skull's location, the team believes the remains ended up there about 10,000 years ago—just before the then dry cave was inundated as sea level began rising. If confirmed, that age would make the skull one of the oldest known remains of an early American, or Paleo-Indian.

Though the skull was found alongside bones of a mastodon and other prehistoric animals in 2007, news of the find was released only late last month, to allow time to properly document the site, train the divers in archaeological practices, and coordinate with authorities.

The divers had previously seen Ice Age animal remains in surrounding caves, but the human skull was a surprise. "That's one of the beauties of exploration—you never know what you're going to find," diver Alberto Nava said.

Now comes the tricky part. "We want to figure out the story of Hoyo Negro and how the human and animal remains got there," said Nave, of the Projecto Espeleológico de Tulum (PET) organization and Global Underwater Explorers (GUE).

Note: National Geographic magazine partially funded archaeological training for the divers on this expedition. Both the magazine and National Geographic News are parts of the National Geographic Society.

Photograph courtesy Daniel Riordan-Araujo

Mastodon Leftovers?

Diver Alex Alvarez examines the remains of a mastodon, found about 20 feet (6 meters) from the human skull during the 2007 Hoyo Negro cave expedition. Other animal bones were found nearby, including the remains of a likely prehistoric bear, according to Alvarez's teammate Alberto Nava.

There are no openings in the cave big enough for a grown mastodon—a smaller, less hairy cousin of the woolly mammoth—to have entered. One possibility, the team says, is that the animal had been hunted and butchered by Paleo-Indian hunters, then carried into the cave in chunks.

Evidence from other sites do seem to confirm that humans once hunted mastodons in North America, according to anthropologist David Meltzer, who wasn't involved in the study.

Overall, the discoveries in Hoyo Negro are "exciting," said Meltzer, a Paleo-Indian expert at Southern Methodist University in Texas.

But, he added, the team's ideas about the bones being 10,000 years old are still "hypotheses to test, rather than conclusions to accept, at this point."

During the 2007 expedition, divers descend into Hoyo Negro—"black hole" in Spanish.

"The name comes from the black holes in space," Nava explained. "When we first entered the place, it was just pitch black everywhere. We almost felt like it was absorbing our light.

"I think most people think of caves as something scary," he added.

"For us, it's a beautiful place. The caves are wide and decorated with stalactites. And the water is so crystal clear that when you look at your hand or your equipment, it looks like you're floating in air."

The skull's shape could offer new insights into where the first Americans migrated from, said Dominique Rissolo, an archaeologist at the Waitt Institute in La Jolla, California. (Waitt and National Geographic collaborate on a grant program.)

"By doing these kinds of analyses, we're able to get a better understanding of which Old World populations these individuals most closely resembled," said Rissolo, who's helping to organize a broader investigation of Hoyo Negro with Mexico's National Institute of Anthropology and History.

For now, though, the skull is still in the upside down position it was found in—the team hasn't touched or moved the remains.

Nava, the cave diver, said, "In any archaeological scene, the context that you find something in is key."

The team hopes at some point to extract a skull sample for testing, but that won't happen until a clear plan is in place.

"Right now our main objective is to protect what is there," Nava said,"and to do the least amount of damage until we can figure out what we're going to do."